1,817 research outputs found
Discontinuous Galerkin Methods for Numerical Weather Prediction: DG in a large-eddy simulation
No full textThe coarse grid of numerical weather prediction and climate models requires parametrization models to resolve atmospheric processes that are smaller than the grid size. For parametrization development, these processes are simulated by a high resolution model. At the Royal Netherlands MeteorologicalInstitute, the Dutch Atmospheric Large-Eddy Simulation (DALES) is used. This three-dimensional high resolution model uses advection schemes that are too diffusive when steep gradients are present. In this thesis, an advection scheme based on the Discontinuous Galerkin (DG) method is implementedfor DALES.The DG method is known to be dispersive. To remove those non-physical oscillations, the moment limiter of Krivodonova is used. Krivodonova constructed the limiter for one- and two-dimensions. In this thesis the moment limiter and limiting order are derived for three-dimensions. DALES is a model based on the finite difference method and uses operational splitting. Therefore, the DG advection scheme needs a mapping from each cell average to all nodal values that are needed for one DG cell, and a mapping back, which we called mapping a and b respectively. Mappings a that are discussed are taking the cell average as value for all nodal points of the DG cell (cell average a), and taking the L -projection of the cell average to the continuous finite element space (L -projection). This thesis describes mappings b that calculate cell averages of nodal DG values (cell average b)and calculate the cell averages of the tendencies of DG values (cell average of tendency). Using cell average a combined with cell average of tendency, made the DG method as diffusive as the first order upwind scheme. Substituting the cell average a method with the L -projection, the DG method becamevery dispersive, meaning that there was not enough diffusion. At last, cell average b was tested with the L -projection. Its numerical results showed that the speed of the advection was slower than the theoretical velocity. Therefore, a method is suggested which does not need mappings. An option couldbe a supergrid that takes multiple DALES cells as a DG cell.Applied Mathematic
Increasing Distributed Generation Penetration using Soft Normally-Open Points
Full text linkThis paper considers the effects of various voltage control solutions on facilitating an increase in allowable levels of distributed generation installation before voltage violations occur. In particular, the voltage control solution that is focused on is the implementation of `soft' normally-open points (SNOPs), a term which refers to power electronic devices installed in place of a normally-open point in a medium-voltage distribution network which allows for control of real and reactive power flows between each end point of its installation sites. While other benefits of SNOP installation are discussed, the intent of this paper is to determine whether SNOPs are a viable alternative to other voltage control strategies for this particular application. As such, the SNOPs ability to affect the voltage profile along feeders within a distribution system is focused on with other voltage control options used for comparative purposes. Results from studies on multiple network models with varying topologies are presented and a case study which considers economic benefits of increasing feasible DG penetration is also given
Dg algebras with enough idempotents, their dg modules and their derived categories
No full textWe develop the theory dg algebras with enough idempotents and their dg modules and show their equivalence with that of small dg categories and their dg modules. We introduce the concept of dg adjunction and show that the classical covariant tensor-Hom and contravariant Hom-Hom adjunctions of modules over associative unital algebras are extended as dg adjunctions between categories of dg bimodules. The corresponding adjunctions of the associated triangulated functors are studied, and we investigate when they are one-sided parts of bifunctors which are triangulated on both variables. We finally show that, for a dg algebra with enough idempotents, the perfect left and right derived categories are dual to each other.The author is highly indebted to Alexander Zimmermann for the careful reading of these notes, for his comments and for his help in improving the presentation. This work is backed by reseach projects from the Ministerio de Economía y Competitividad of Spain(MTM201346837-P and MTM201677445-P) and the Fundación ’Séneca’ of Murcia(19880/GERM/15), both with a part of FEDER funds. We thank these institutions for their support
Life cycle comparison of petroleum- and bio-based paper binder from distillers grains (DG)
No full textAbstractThis study presents a comparative cradle-to-gate life cycle assessment (LCA) of distillers grain (DG) gum, a bio-based paper coating binder, and polyvinyl alcohol (PVA). Non-renewable energy use, greenhouse gas (GHG) emissions, and eutrophication potential were assessed for each binder. Economic, mass, and energy allocation were used to allocate the impacts of DG gum production with co-products (ethanol and livestock feed). DG production non-renewable energy use (269 to 183MJ) surpassed that associated with PVA production (168MJ). GHG emissions from DG gum production under mass and energy allocations were 28% and 37% lower than PVA production emissions, respectively. Corn cultivation is responsible for 55% to 78% of the eutrophication impacts of DG gum production under energy and economic allocation, respectively. Changes to natural gas consumption and fertilizer runoff had the largest influence on total energy use, GHG emissions, and eutrophication potential of DG gum production
The DG-category of secondary cohomology operations
Full text linkWe study track categories (i.e., groupoid-enriched categories) endowed with additive structure similar to that of a 1-truncated DG-category, except that composition is not assumed right linear. We show that if such a track category is right linear up to suitably coherent correction tracks, then it is weakly equivalent to a 1-truncated DG-category. This generalizes work of the first author on the strictification of secondary cohomology operations. As an application, we show that the secondary integral Steenrod algebra is strictifiable
Coderived and contraderived categories of locally presentable abelian DG-categories
Full text linkThe concept of an abelian DG-category, introduced by the first-named author in arXiv:2110.08237, unites the notions of abelian categories and (curved) DG-modules in a common framework. In this paper we consider coderived and contraderived categories in the sense of Becker. Generalizing some constructions and results from the preceding papers by Becker arXiv:1205.4473 and by the present authors arXiv:2101.10797, we define the contraderived category of a locally presentable abelian DG-category with enough projective objects and the coderived category of a Grothendieck abelian DG-category . We construct the related abelian model category structures and show that the resulting exotic derived categories are well-generated. Then we specialize to the case of a locally coherent Grothendieck abelian DG-category , and prove that its coderived category is compactly generated by the absolute derived category of finitely presentable objects of , thus generalizing a result from the second-named author\u27s preprint arXiv:1412.1615. In particular, the homotopy category of graded-injective left DG-modules over a DG-ring with a left coherent underlying graded ring is compactly generated by the absolute derived category of DG-modules with finitely presentable underlying graded modules. We also describe compact generators of the coderived categories of quasi-coherent matrix factorizations over coherent schemes.LaTeX 2e with xy-pic and one mathb symbol; 76 pages, 1 figure; v.2: a discussion of quasi-coherent matrix factorizations over coherent schemes added in a new Section 9; new Corollary 0.4, Sections 1.10 and 2.7, Examples 3.15, 6.12, 7.8, 8.8, and 8.10 inserted; a paragraph added at the end of Section 2.1, 4th paragraph of the introduction expanded; v.3: several misprints correcte
DG 3 in memoriam
No full textThe manuscript DG 3 in Uppsala was destroyed in the town-fire 1702. In the present study, the author tries to find out what the manuscript contained, as far as it can be concluded on basis of Jonas Rugman’s translation in Norlands Chrönika 1677. The present author opposes the common belief that Rugman used the Norwegian (Danish) translation made by Peder Claussøn and published by Ole Worm 1633. On the contrary, the author argues that Rugman did not know of the existence of this translation. If he indeed knew about it, he chose not to use it. The short pieces of Sverris saga and the Skáldatal obviously following Claussøn’s text, did so because the owner in Denmark, Stephan Stephanius, had copies of those pieces made from the printed version of 1633
Multiple DG Placements in Distribution System for Power Loss Reduction Using PSO Algorithm
No full textAbstractOptimal placement and optimal sizing of Distributed Generation (DG) for the sake of reduction in power loss and improvement of voltage profile in distribution networks are investigated in this paper. Particle Swarm Optimization (PSO) algorithm is used to find out the best location and optimal size of DG. Complete analysis is carried out on IEEE 33-bus and IEEE 69-bus radial distribution systems. Each system is considered for two different cases and comparative results obtained will demonstrate the effectiveness of the proposed method as far as placement, sizing of DG and minimization of power losses are concerned
Milnor descent for cohesive dg-categories
Full text linkWe show that the functor from curved differential graded algebras to
differential graded categories, defined by the second author in [B], sends
Cartesian diagrams to homotopy Cartesian diagrams, under certain reasonable
hypotheses. This is an extension to the arena of dg categories of a
construction of projective modules due to Milnor. As an example, we show that
the functor satisfies descent for certain partitions of a complex manifold.Comment: 21 page
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